Transcript Slide 1

Chapter 2
Are We Alone in the Universe?
Water, Biochemistry, and Cells
Fourth Edition
BIOLOGY
Science for Life | with Physiology
Colleen Belk • Virginia Borden Maier
© 2013 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc.
PowerPoint Lecture prepared by
Jill Feinstein
Richland Community College
Requirements for Life:
1. water
2. food
3. oxygen
4. heat
5. pressure
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2.1 What Does Life Require? FOOD
the food we ingest as humans is made up of
macromolecules
Macromolecules: very large compounds made up
of smaller molecules joined together
in biochemistry – 4 types of macromolecules
these macromolecules are found in living organisms
 many of which we eat
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Macromolecules
Macromolecules:
 Carbohydrates
 Proteins
 Lipids
 Nucleic Acids
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Structure and Function of Macromolecules
 Carbohydrates: molecules of
carbon, oxygen, and hydrogen
 Major source of energy for cells
 Monosaccharides or simple
sugars are building blocks for
carbohydrates
 Disaccharides are composed of
two monosaccharides joined
together
 Polysaccharides are composed of
many monosaccharides joined
together
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Monosaccharides:
- in aqueous solutions –monosaccharides are not linear
-they form rings
-three ways to represent the ring structure of a monosaccharide
3. Simplest form
1. Molecular
ring form
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2. Abbreviated ring structure
A. Simple carbohydrates
• disaccharide = two monosaccharides bound together
-formed by a dehydration synthesis reaction – results in the removal of a
water molecule
-broken up by a hydrolysis reaction – requires you to put the water back in
e.g. glucose + glucose = maltose
e.g. glucose + fructose = sucrose
e.g. glucose + galactose = lactose
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B. Complex carbohydrates or Polysaccharides:
•a polysaccharide is an example of a polymer
•polymer – compound made of repeating units
called monomers
•monomer = monosaccharide
•some polysaccharides serve as storage
materials – hydrolyzed into individual
monosaccharides – for energy production
-animals = glycogen (highly branched
polymer of glucose monomers)
-plants = starches (glucose polymers but with
different bonds holding them together)
•others serve as structural or building materials
• plants = cellulose (glucose polymers
but with different bonds holding them
together)
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Amylopectin
Amylose
Glycogen
Complex carbohydrates: High fructose corn syrup
(HFCS)
First described in 1957 by Richard Marshall and Earl Kooi

Required the use of arsenic to make in large quantities
Perfected for commercial use in 1961 – Yamanaka
HFCS = any corn syrup that has undergone enzymatic processing to
convert some of its glucose monomers into fructose

HFCS55 – 55% fructose and 42% glucose (similar to honey)

HFCS42 – 42% fructose and 53% glucose
Cheaper than sucrose due to import tariffs on sugar cane and/or sucrose
Used because fructose is sweeter than glucose
No difference between HFCS and sucrose in terms of satisfaction and
health effects??

Typical American weighs 25 lbs more than 25 yrs ago

HFCS entered into the American diet in 1975
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3. Proteins
• nearly every dynamic function of a living organism depends on
proteins
•Greek – proteios = “first place”
•more than 50% of the dry mass of most cells
•numerous roles:
• structural – support of cells and tissues
• storage - energy source
• transport across cell membranes
• hormones and their receptors – signaling
• chemical messengers - signaling
• antibodies - defense
• metabolic role - enzymes
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Structure and Function of Macromolecules
 Proteins: polymers of amino acids;
joined by peptide bonds
Side chain (R group)
 carbon
 Proteins are made up of carbon,
oxygen, hydrogen, and nitrogen.
 There are 20 different amino acids,
with different chemical properties.
 Different combinations of amino
acids give proteins different
properties.
 amino acids are joined by
dehydration synthesis reactions
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Amino
group
Carboxyl
group
• amino acids joined together by a dehydration synthesis reaction
forming a peptide bond = between the NH2 of 1 a.a. and the COOH
of the next amino acid
Side
chains
Back- bone
2 a.a.  dipeptide
3 a.a.  tripeptide
New peptide
bond forming
4 or more a.a.  polypeptide
Carboxyl end
(C-terminus)
Amino end
(N-terminus)
New Peptide
bond
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Sickle-Cell Disease: A Change in Primary Protein
Structure
A slight change in primary structure can affect a protein’s
structure and ability to function
Sickle-cell disease, an inherited blood disorder, results from a
single amino acid substitution in the protein hemoglobin
Sickle-cell hemoglobin
Normal hemoglobin
Primary
Structure
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1
2
3
4
5
6
7
Secondary
and Tertiary
Structures
Quaternary
Structure
 subunit


Exposed
hydrophobic
region
 subunit

10 m

Sickle-cell
hemoglobin

Red Blood
Cell Shape
Molecules do not
associate with one
another; each carries
oxygen.
Normal
hemoglobin

1
2
3
4
5
6
7
Function
Molecules crystallize
into a fiber; capacity
to carry oxygen is
reduced.


10 m
Structure and Function of Macromolecules
• proteins have four levels of
organization:
• 1. Primary – amino acid sequence
of the polypeptide chain
•sequence is determined by the
DNA sequence found within a
gene
• 2. Secondary – coils and pleats
due to interactions among the AAs
• 3. Tertiary – 3D structure
• 4. Quaternary – more than one
polypeptide chain “woven”
together
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Structure and Function of Macromolecules
 Lipids: hydrophobic; composed mostly of carbon and hydrogen
 energy source for cells
 Three types:
 1. Fat is composed of a glycerol molecule joined with 3 fatty acids
 2. Steroids are a four carbon ring structure
 e.g.cholesterol, estrogen and testosterone
 3. Phospholipids are composed of a glycerol molecule, 2 fatty acids called
“tails” and a phosphate group called a “head group”
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1. Fats
•
•
•
•
energy supply
most plentiful lipids in your body
composed of C, H and O
“building blocks” = 3 fatty acid chains (hydrocarbons
usually from 16 to 18 carbons)
PLUS 1 glycerol molecule
fatty acid
fatty acid
fatty acid
glycerol portion
fatty acid portion
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• fatty acids -differ in chain length with each fat
-ALSO - differ in the location and number of
double bonds within the hydrocarbon chain
1. single C bonds - saturated
carboxyl gp
• Saturated fatty acids have the maximum number of
hydrogen atoms possible and no double bonds
• solids at room temperature
– except for palm oil and coconut oil
• animal fats and butter
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2. double C bonds - unsaturated
monounsaturated:
1 double bond
polyunsaturated:
2 or more double bonds
• Unsaturated fatty acids have one or more double bonds in the
hydrocarbon chains
• are liquid at room temperature
• oils
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2. double C bonds - unsaturated
monounsaturated:
1 double bond
polyunsaturated:
2 or more double bonds
-Polyunsaturated fatty acids & health
-important in regulating cholesterol levels - lower LDL levels in the
blood
-increase calcium utilization by body –good for bone density
- reduce inflammation – role in preventing arthritis?
- promote wound healing
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(a) Saturated fat
(b) Unsaturated fat
double bond
causes bending in the
fatty acid chain.
•
at room temperature – the molecules of a saturated fat are packed closely
together
•
•
•
the fatty acid tails are more flexible
forms a solid
the molecules of an unsaturated fat cannot pack closely together enough to
solidify
•
the C=C bonds produce a “kink” in the fatty acid chain making it difficult to pack
them together
• if the fat contains one fatty acid that is unsaturated – then the fat is considered
unsaturated
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Education,at
Inc.room temperature
• liquid
2. Phospholipids
•modified fat – replace one fatty acid with a phosphate group (negative electrical
charge)
• phosphate group  hydrophilic “head”
• fatty acid groups  hydrophobic “tails”
• when added to water – self-assemble and form a form a phospholipid
bilayer – major component of the plasma membrane
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3. Steroids
• backbone is called cholesterol = 4 fused carbon rings
• cholesterol is synthesized in the liver
• modified in other organs
• e.g. testosterone – cholesterol is modified in the testes
• diversity through attached functional groups
e.g. testosterone, estrogen, aldosterone
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Structure and Function of Macromolecules
 Nucleic acids: polymers of nucleotides
 Nucleotide: sugar + a phosphate group + a nitrogenous
base
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Figure 2.15c
Nitrogenous bases
 there are two families of
nitrogenous bases:
Pyrimidines
Cytosine
(C)
Thymine
(T, in DNA)
Uracil
(U, in RNA)
Purines
Adenine (A)
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Guanine (G)
1. Pyrimidines
(cytosine, thymine,
and uracil) have a
single six-membered
ring
2. Purines (adenine and
guanine) have a sixmembered ring fused
to a five-membered
ring
• Nucleic acids can be linked together to form a polynucleotide chain - formed by a
dehydration synthesis reaction
•bond forms between the phosphate of 1 nucleotide and the sugar of the next
Sugar-phosphate backbone
5 end
5C
3C
phosphodiester
bond
5C
3C
3 end
(a) Polynucleotide, or nucleic acid
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• two major types of polynucleotide
chains:
1. RNA
2. DNA
Structure and Function of Macromolecules
 Nucleotides are of two types: RNA and DNA,
depending on the sugar in the nucleotide
1. RNA sugar = ribose
2. DNA sugar = deoxyribose
HOCH2
O
OH
H
H
OH
OH
ribose
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HOCH2 O
OH
H
H
OH
H
deoxyribose
A. RNA
single polynucleotide chain
bases: A, C, G and uracil (U) in place of T
numerous types found in cells – the most common is
called mRNA or messenger RNA (plays a role in gene
expression)
B. DNA
double polynucleotide chain = double helix
2 chains held together by hydrogen bonds between the
bases
bases pair up in a complementary fashion
A=T
C G
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Structure and Function of Macromolecules
 DNA is the hereditary material
in nearly all organisms.
 the structure of a DNA
molecule is a double helix.
 the sugar-phosphate backbone
found on the outside of the helix
 the bases found on the inside
 the helix is held together by
hydrogen bonds between the
bases
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Structure and Function of Macromolecules
Animation: Nucleic Acids
Right-click slide / select “Play”
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Structure and Function of Macromolecules
 bonding between
bases on opposite
strands follows
strict base-pairing rules:
 A with T – double H bonds
 G with C – triple H bonds
 so regions of the helix with GC base pairs are held
together stronger that regions with AT base pairs
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Genomics
study of the genome of animals and humans and their relationship to the function
of the organism
Human Genome Project – June 1990
genome = genetic makeup of an individual (genes + “junk DNA”)
humans – 23 chromosome pairs totaling 3.2 billion nucleotides
most humans share 99.9% of their genome
therefore unique attributes come from only 0.1% of a human’s genome (1 in 100
nucleotides)
over 50% of our genome does not code for any protein = junk DNA
only about 40,000 active protein-coding genes in our genome (only 1.5% of the
human genome!!!)
average gene = 3000 base pairs
dystrophin – largest human gene = 2.4 million nt’s
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c. ATP
individual n.t’s can have metabolic functions
e.g. adenosine = adenine + ribose
-adenine modified by adding three phosphates
major source of ATP = breakdown of glucose
1 glucose molecule
glycolysis
Kreb’s cycle
oxidative phosphorylation
36 ATP
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